1. Technical Field
The present disclosure relates to a vehicle display device for displaying a virtual image on a field of view of a driver, and particularly relates to a technique for calculating relative position and orientation between a display device and a viewpoint detecting camera for detecting a viewpoint of an observer of the virtual image.
2. Description of Related Art
By mounting a Head Up Display (HUD) in a vehicle, a virtual image can be displayed on a field of view of a driver, and a sight line movement is reduced, whereby a burden of a driver in reading information can be reduced.
In addition, more information can be provided to the driver by an Augmented Reality (AR) display such as marking and highlighting an obstacle ahead.
When such an AR display is performed, if a drawing object and drawing contents are not in a predetermined position relationship as seen from the driver, this causes annoyance and false recognition, and therefore it is desirable that a viewpoint position of the driver is detected so that a drawing position is accordingly changed. Typically, a viewpoint detecting camera is installed in a vehicle compartment, whereby the viewpoint position of the driver is detected.
However, there are error factors in both of the viewpoint detecting camera and the HUD such as unevenness at the time of assembly and displacement at the time of mounting to a vehicle body, and there is a high possibility that the position relationship between the viewpoint detecting camera and the HUD is different from the assumption at the time of design. Therefore, it is desirable that a relative orientation between the viewpoint detecting camera and the HUD is measured by any means after the mounting, and that the drawing is performed based on the measured relative orientation during the drawing.
On the other hand, Patent Literature (PTL) 1 (see Japanese Patent Unexamined Publication No. 2009-262666) discloses a method in which a mirror is installed in the position of the eye of the driver, and the position relationship between the viewpoint detecting camera and the HUD is adjusted while looking at the image of the mirror captured by the viewpoint detecting camera.